Scapulohumeral Rhythm

The Scapulohumeral Rhythm allows our shoulders to be very functional and have full ROM. The Scapulohumeral Rhythm is the coordinated movement between the humerus and the scapula. The ratio for this movement is 2:1. Therefore, the humerus will move 120 degrees on the glenohumeral joint and the scapula will move 60 degrees on the scapulothoracic joint. Therefore, for full range of motion you need to have 180 degrees of movement. The humeral head must rotate laterally for full ROM. If you do not have full ROM at the scapula or humerus, you will not have full motion. The motion will need to be split between the two. The relationship of the opposing joints (GH and ST) results in decreased shear forces. Full ROM also allows good length-tension relationships. If the Scapulohumeral Rhythm is off, it would typically cause pain and may be a sign of impingement. Some signs of impingement are bone spurs, change in the shape of the acromion, scapular movement dysfunction and humeral movement dysfunction. All of these can result in decreased ROM and ultimately can prevent the Scapulohumeral Rhythm from functioning as needed. When the Scapulohumeral Rhythm is functioning normally, it eliminates injury that may occur to the glenohumeral joint and surrounding structures. In a clinical viewpoint, you will need to know how to detect decreased ROM and also what interventions will be able to help your client in gaining back their full ROM.